1. Field of Invention
The present general inventive concept relates to devices that are useful in the manufacture of vehicle tires. More particularly, the present general inventive concept relates to an improved transfer ring useful in the manufacture of vehicle tires.
2. Description of the Related Art
The manufacture of a vehicle tire commonly includes the steps of forming a tire carcass, forming a toroid-shaped belt and tread “package” of the tire separately from the carcass, and thereafter marrying the belt and tread package to the tire carcass to form a “green” tire. The green tire is thereafter treated to form the tread and various other features of a finished tire. Other supplementary steps, such as bonding the belt and tread package to the tire carcass (often referred to as “stitching” the belt and tread package), may be performed during the course of, or following, one or more of the aforementioned steps.
Formation of a belt and tread package of a tire is typically accomplished using a belt and tread drum, of the type disclosed in U.S. Pat. No. 6,013,147. Such a belt and tread drum typically has an outer cylindrical surface, or circumference, about which one or more layers of the tire belt material (comprising, for example, reinforcement cords embedded in a polymeric binder) are laid to define the belt and tread package. The circumference of the belt and tread drum is preferably capable of expanding and contracting to allow, for example, removal of a completed belt and tread package from the drum. A completed belt and tread package is typically essentially nonexpandable radially. However, a completed belt and tread package is typically flexible to the extent that, when unsupported, the toroid-shaped belt and tread package will deform and sag under the influence of gravity. Also, desirably, the adjustable circumference of the belt and tread drum enables a single drum to be used to form belt and tread packages of alternative diameters.
In the manufacture of vehicle tires, a tire carcass is typically fabricated using a tire building drum, of the type described in U.S. Pat. No. 6,457,505. Such a tire building drum typically defines a radially expandable and contractible cylindrical working surface, similar to the above-discussed belt and tread drum, upon which a tire carcass is formed. Subsequent to the formation of the tire carcass on the cylindrical working surface, such tire carcass typically is transferred to an expansion drum, of the type discussed in U.S. Pat. No. 6,602,372. The tire carcass is positioned surrounding the expansion drum, and a portion of the tire carcass is overlaid with the belt and tread package. The tire carcass is then inflated to a toroid shape resembling, though often not identical to, the shape of a finished tire. While the tire carcass is inflated, the belt and tread package is stitched to the tire carcass.
In the above-described process, the steps of transferring a tire carcass from a tire building drum to an expansion drum and transferring a belt and tread package to a tire carcass for stitching are typically both accomplished using one or more transfer rings, of the type described in U.S. Pat. No. 8,091,602. Such a transfer ring typically includes a plurality of “shoe” segments having arced interior surfaces which collectively form a segmented, radially-inwardly-facing cylindrical surface suitable for grasping and holding a tire carcass and/or a belt and tread package. Each shoe segment is mounted on an appropriate linkage such that the shoes are collectively radially expandable and contractible with respect to one another, such that the diameter of the segmented, radially-inwardly-facing cylindrical surface can be expanded to fit over a tire carcass and/or belt and tread package, contracted to grasp the tire carcass or belt and tread package for transfer, and then re-expanded to release the tire carcass or belt and tread package following transfer.
When a transfer ring is used as described above to transfer a tire carcass and/or belt and tread package (hereinafter, collectively, “tire component,”), it is not uncommon for the transfer ring to be configured such that the shoes apply considerable pressure to exterior surfaces of the tire component, in part to assist in maintaining a uniform toroid shape of the tire component during transfer. Such high pressures applied to the exterior surfaces of the tire component can result in at least a portion of the arced interior surfaces of the shoes becoming imprinted in the tire component, resulting in the formation of imprints of the interior surfaces of the shoes, and corresponding bulges adjacent the imprints, in the tire component. When a finished tire that includes these imprints and corresponding bulges rolls across a surface, sequential contact of the alternating imprints and bulges in the tire components with the surface can, in certain circumstances, result in undesirable performance features of the finished tire, such as for example vibration and/or resonance of the rolling tire. Such vibration and/or resonance can result in undesirable noise and/or shaking of the tire, increased wear and shortened life of the tire, and in some extreme instances, catastrophic failure of the tire.
In several designs of transfer rings, the above-discussed problem of resonance of a finished tire due to sequential contact between a surface on which the tire is rolled and bulges and imprints of shoe interior surfaces on the tire components is partially addressed by providing a prime number of shoes to form the radially-inwardly-facing cylindrical surface of the transfer ring. For example, in certain transfer ring designs, eleven shoes are provided to define the radially-inwardly-facing cylindrical surface of the transfer ring. In other designs, thirteen shoes are provided to define the radially-inwardly-facing cylindrical surface of the transfer ring. By providing a prime number of shoes to form the radially-inwardly-facing cylindrical surface, the same prime number of resultant imprints and corresponding bulges are formed in the transferred tire components. Thus, the ability for the tire to establish a resonating frequency when rolling across a surface due to sequential contact of the alternating imprints and bulges against the surface is limited to certain frequencies which are compatible with the prime number of shoes of the transfer ring. In many tire designs, the limited accessibility of such compatible frequencies at typical operating speeds of the tire result in low amounts of vibration. However, in several designs, vibration at such frequencies which is sufficient to disrupt performance of the tire is attainable at certain high speeds of the tire. The high speeds necessary to establish such vibrations are typically outside of the range of speeds for which the particular tire is recommended for use.
Notwithstanding the above, in certain high-speed tire applications, such as for example certain applications of tires used in the landing gear for aircraft, it is possible for tires which were formed using transfer rings having a prime number of shoes to be rolled at speeds which allow for the development of sufficient resonation of the tire which is strong enough to negatively impact performance of the tire and/or to reduce the overall effective life of the tire. Accordingly, a tire transfer ring which includes alternate or additional features for limiting resonance of a tire manufactured using the transfer ring is desired.